1. Field of the Invention
This invention relates to a process for preparing oil-soluble nitrogen-containing compounds which are particularly useful as additives for fuel oils and lubricating oils, thus imparting good detergency, dispersability, corrosion resistance, rust-preventing property and lubricity to the oils. The above-mentioned nitrogen-containing compounds cover not only nitrogen-containing compounds having improved properties but also both nitrogen and boron-containing compounds having more improved properties.
2. Description of the Prior Art
It is known that when certain types of basic compounds having nitrogen atoms therein are added to fuel oils and lubricating oils, the oils will be provided with various properties such as, for example, excellent detergency, dispersability, corrosion resistance, rust-preventiveness and friction reducibility.
For instance, alkenyl succinimides of alkylene polyamines described in U.S. Pat. No. 3,172,892 and copolymers of methacrylic esters and nitrogen-containing basic monomers described in U.S. Pat. No. 2,737,496 are known as a good detergent-dispersant of petroleum products. Aliphatic amines such as oleylamine have wide utility as a good corrosion preventive or a friction reducing agent for petroleum products. These nitrogen-containing compounds are so-called oil-soluble surface active agents and consist generally of long-chain organic residue portions serving as oleophilic groups and nitrogen-containing compound portions serving as polar groups. A variety of such compounds have been developed using different types of oleophilic groups and polar groups and different manners of introduction thereof. However, the introduction of the long-chain organic residue, used as the oleophilic group, into the resulting nitrogen-containing compounds is not easy especially when the oleophilic group is a long-chain hydrocarbon group. Generally, two or three reaction steps are required for the introduction. For instance, in the above-mentioned U.S. Pat. No. 3,172,892, the alkenyl succinimides of alkylene polyamines are obtained by the steps of cation polymerization of isobutylene to obtain polybutene, reaction of the polybutene with maleic anhydride to obtain polybutenylsuccinic anhydride, and further reaction with alkylene polyamines to obtain the alkenyl succinimides.
Thus, the conventional processes for preparing oil-soluble nitrogen-containing compounds having long-chain hydrocarbon groups present the problem of needing a number of reaction steps. With the alkenyl succinimides, the imido bonding adversely influences the demulsibility as an additive.
Moreover, it is known that when the nitrogen-containing compounds are borated or coordinated with boron, they will be further improved in corrosion resistance, rust-preventive property and friction reducibility while maintaining their functions as a detergent and a dispersant. In addition, oxidation and wear resistances are imparted to the compounds.
For instance, U.S. Pat. Nos. 3,087,936, 3,254,025 and 3,322,670 disclose borated alkenylsuccinimides which have not only good detergency and dispersability derived from the alkenylsuccinimides, but also high corrosion and wear resistances. Compounds obtained by borating aliphatic amines such as oleylamine have been improved in friction reducibility of the original aliphatic amines and are newly provided with corrosion resistance.
When oil-soluble nitrogen-containing compounds such as alkenyl succinimides and oleylamine are borated or coordinated with boron, the resulting compounds show greatly improved functions as additives for petroleum products. However, these borated compounds have the following problems.
The borated alkenyl succinimides have very poor demulsibility similar to the starting alkenylsuccinimides and thus, cannot be used as additives for lubricating oils such as working oils or gear oils, which require high demulsibility. Further, these borated compounds may unfavorably cause emulsion sludges when used in engine oils.
On the other hand, borated compounds of aliphatic amines such as oleylamine are low in oil solubility due to the boration, so that it is almost impossible to add them to fuel oils or lubricating oils in large amounts.
As will be appreciated from the foregoing, the known oil-soluble nitrogen and boron-containing compounds present many problems with respect to their properties.